The purpose of this research grant is to characterize and compare human pancreatic carboxypeptidase B and human plasma carboxypeptidase N. The study will include information on the active centers of both enzymes using affinity labeling reagents, group specific chemical reagents, and byproduct analog competitive inhibitors. It will eventually include isolation of active site peptides and immunochemical comparisons to determine the extent of structural homology. This information will help to clarify the physiological importance of carboxypeptidase N as a kininase and anaphylatoxin inactivator in the blood of mammals.